STP1046V2

Effects of Radiation on KIc Curves for High Copper Welds

The fifth irradiation series in the Heavy-Section Steel Technology (HSST) Program is aimed at obtaining a statistically significant fracture toughness data base on two weldments with high copper contents to determine the shift and shape of the KIc curve as a consequence of irradiation. The program includes irradiated Charpy V-notch impact, tensile, and drop-weight specimens in addition to compact fracture toughness specimens. Compact specimens (CS) with thicknesses of 25.4, 50.8, and 101.6 mm (1TCS, 2TCS, and 4TCS, respectively) have been irradiated. Additionally, unirradiated 6TCS and 8TCS have been tested to attain the same KIc measuring capacity as the irradiated specimens. The materials for this irradiation series are two weldments fabricated from special heats of weld wire with copper added to the melt. One lot of Linde 0124 flux was used for all the welds. Copper levels for the two welds are 0.23 and 0.31 wt% while the nickel contents are 0.60 wt%.

Twelve capsules of specimens have been irradiated in the poolside facility of the Oak Ridge Research Reactor (ORR) at a nominal temperature of 288°C and an average fluence of about 1.6×1019neutrons/cm2 (>1 MeV). Performance of the test plan was a cooperative effort between Oak Ridge National Laboratory (ORNL) and Materials Engineering Associates (MEA). The test results show a high degree of scatter in the transition temperature region, which causes a large uncertainty in the fracture toughness predictions for the large specimens. Weibull and standard statistical analyses are used for test temperature selection and data analyses. The Charpy 41-J (30-ft · lb) temperature shifts are about the same as the corresponding drop-weight nil-ductility transition temperature shifts. Preliminary analyses indicate that the shifts in fracture toughness are somewhat greater than those of the Charpy and drop-weight tests and that the KIc curve changes shape.